This application is based on an application No. 2000-097302 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a data broadcast apparatus that multiplexes additional data with data of a TV program and broadcast them so that the additional data is presented to a viewer with the TV program. The invention in particular relates to techniques of controlling presentation timing for additional data.
2. Related Art
In recent digital broadcasting, additional data such as character information is multiplexed with program data such as video and audio and broadcasted.
In general, the same or renewed additional data is repeatedly multiplexed with program data and broadcasted, with a cycle of about 5 to 10 seconds.
A data broadcast apparatus that performs such digital broadcasting is disclosed in Japanese Laid-Open Patent application No. H10-313449.
The most common method used for periodic broadcast of additional data is the Data Carousel (hereafter simply called xe2x80x9ccarousel methodxe2x80x9d) specified by the internationally standardized DSM-CC (Digital Storage Mediaxe2x80x94Command and Control) (described in detail in Information Technologyxe2x80x94Generic Coding of Moving Pictures and Associated Audio: DSM-CCxe2x80x94ISO/IEC 13818-6). Broadcast of additional data according to the carousel method has been adopted for BS digital broadcasting service and the like in Japan (described in detail in the ARIB STD-B24 specification xe2x80x9cData Broadcast Coding and Transmission in Digital Broadcastingxe2x80x9d).
With this method of repeatedly transmitting additional data, a reception apparatus can receive only necessary additional data and reproduce it, with it being possible to utilize enormous amounts of information without a large-capacity memory.
To renew additional data broadcasted using the carousel method, a method called carousel updating is employed. Carousel updating is a technique in which a broadcast apparatus estimates a time period required to receive the next additional data, and switches the broadcasting from the present additional data to the next additional data the estimated time period before a reception apparatus switches the presentation from the present additional data to the next additional data. This is described in detail in Japanese Laid-Open patent application No. H10-313449.
However, since there are variations in the time period required to receive additional data, the above technique has a problem that there is a large timing error for changing from the present additional data to the next additional data in the reception apparatus.
This timing error depends on the cycle in which additional data is repeatedly transmitted. For instance, when the cycle is 8 seconds, the time period taken to receive the additional data is about 8 seconds at the maximum but within 1 second at the minimum. In this case, there is a timing error of 7 seconds or more. With such a low degree of precision, the above technique is not applicable when presenting additional data of a commercial program with a short broadcast time period of about 15-30 seconds, though it is still applicable when presenting additional data of a main program with a long broadcast time period of 30 minutes or more.
The object of the present invention is to provide a data broadcast apparatus, method, and program that can control the timing of changing additional data presented to a viewer with greater precision.
The above object can be fulfilled by a data broadcast apparatus for repeatedly broadcasting broadcast data using a carousel method, to a reception apparatus which stores the broadcast data into a memory and reproduces the broadcast data stored in the memory, including: an acquiring unit for acquiring a plurality of sets of broadcast data for each of which a reproduction start time is specified; a generating unit for generating carousel data including the plurality of sets of broadcast data acquired by the acquiring unit; a carousel data broadcasting unit for repeatedly broadcasting the carousel data using the carousel method, beginning at an earliest reproduction start time out of a plurality of reproduction start times of the plurality of sets of broadcast data; and an instruction broadcasting unit for broadcasting, for each set of broadcast data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of broadcast data at a reproduction start time specified for the set of broadcast data.
With this construction, broadcast data to be reproduced earlier and broadcast data to be reproduced later in the reception apparatus are repeatedly broadcasted together, and an instruction which indicates to start the reproduction of the latter broadcast data at a reproduction start time specified for the latter broadcast data is broadcasted.
Since the reception apparatus can store the latter broadcast data in a memory beforehand and reproduce it at the reproduction start time, there is almost no delay in reproduction caused by the time taken to receive the latter broadcast data. Thus, the broadcast apparatus can control the timing of changing broadcast data presented to a viewer, with greater precision.
Also, it becomes unnecessary to frequently change the contents of carousel data broadcasted, with it being possible to lighten the burden on the broadcast apparatus.
Here, the instruction broadcasting unit may further broadcast a storage instruction which indicates to the reception apparatus to store the set of broadcast data into the memory before the reproduction start time.
With this construction, an instruction which indicates to store the latter broadcast data into the memory before the reproduction start time is broadcasted.
Accordingly, the reception apparatus can store necessary broadcast data only when required, with it being possible to economize memory usage in the reception apparatus.
Here, the instruction broadcasting unit may further broadcast a deletion instruction which indicates to the reception apparatus that the set of broadcast data can be deleted from the memory after the reproduction ends.
With this construction, an instruction which indicates that the latter broadcast data can be deleted from the memory after the reproduction ends is broadcasted.
Accordingly, the reception apparatus can delete from the memory broadcast data which becomes unnecessary, with it being possible to economize memory usage in the reception apparatus.
Here, the instruction broadcasting unit may broadcast the reproduction instruction as an event message or a module which has a particular identifier.
With this construction, the instruction to start the reproduction of the latter broadcast data is broadcasted as an event message or a module having a particular identifier.
This makes it possible to implement the invention with conventional reception apparatuses.
The above object can also be fulfilled by a data broadcast apparatus for (a) continuously broadcasting program data during a broadcast time slot to a reception apparatus, and (b) repeatedly broadcasting additional data associated with the program data during the broadcast time slot using a carousel method, to the reception apparatus which stores the additional data into a memory and reproduces the additional data stored in the memory, including: an acquiring unit for acquiring a plurality of sets of program data for each of which a broadcast time slot is specified, and a plurality of sets of additional data which are respectively associated with the plurality of sets of program data; a generating unit for generating carousel data including the plurality of sets of additional data acquired by the acquiring unit; a data broadcasting unit for (a) continuously broadcasting, during a broadcast time slot of each set of program data, the set of program data, and (b) repeatedly broadcasting the carousel data using the carousel method, beginning at the start of an earliest broadcast time slot of a plurality of broadcast time slots of the plurality of sets of program data; and an instruction broadcasting unit for broadcasting, for each set of additional data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of additional data at the start of a broadcast time slot specified for a set of program data associated with the set of additional data.
With this construction, additional data to be reproduced earlier and additional data to be reproduced later in the reception apparatus are repeatedly broadcasted together, and an instruction which indicates to start the reproduction of the latter additional data at the start of a broadcast time slot specified for program data associated with the latter additional data is broadcasted.
Since the reception apparatus can store the latter additional data in a memory beforehand and reproduce it at the start of the broadcast time slot, there is almost no delay in reproduction caused by the time taken to receive the latter additional data. Thus, the broadcast apparatus can control the timing of changing additional data presented to a viewer, with greater precision.
Here, the instruction broadcasting unit may further broadcast a storage instruction which indicates to the reception apparatus to store the set of additional data into the memory before the start of the broadcast time slot.
With this construction, an instruction which indicates to store the latter additional data into the memory before the start of the broadcast time slot is broadcasted.
Accordingly, the reception apparatus can store necessary additional data only when required, with it being possible to economize memory usage in the reception apparatus.
Here, the instruction broadcasting unit may further broadcast a deletion instruction which indicates to the reception apparatus that the set of additional data can be deleted from the memory after the reproduction ends.
With this construction, an instruction which indicates that the latter additional data can be deleted from the memory after the reproduction ends is broadcasted.
Accordingly, the reception apparatus can delete from the memory additional data which becomes unnecessary, with it being possible to economize memory usage in the reception apparatus.
Here, the instruction broadcasting unit may broadcast the reproduction instruction as an event message or a module which has a particular identifier.
With this construction, the instruction to start the reproduction of the latter additional data is broadcasted as an event message or a module having a particular identifier.
This makes it possible to implement the invention with conventional reception apparatuses.
The above object can also be fulfilled by a computer program embodied on a computer readable medium for use with a computer, for repeatedly broadcasting broadcast data using a carousel method to a reception apparatus which stores the broadcast data into a memory and reproduces the broadcast data stored in the memory, the computer program including: an acquiring step for acquiring a plurality of sets of broadcast data for each of which a reproduction start time is specified; a generating step for generating carousel data including the plurality of sets of broadcast data acquired in the acquiring step; a carousel data broadcasting step for repeatedly broadcasting the carousel data using the carousel method, beginning at an earliest reproduction start time out of a plurality of reproduction start times of the plurality of sets of broadcast data; and an instruction broadcasting step for broadcasting, for each set of broadcast data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of broadcast data at a reproduction start time specified for the set of broadcast data.
The above object can also be fulfilled by a data broadcast method for repeatedly broadcasting broadcast data using a carousel method to a reception apparatus which stores the broadcast data into a memory and reproduces the broadcast data stored in the memory, the data broadcast method including: an acquiring step for acquiring a plurality of sets of broadcast data for each of which a reproduction start time is specified; a generating step for generating carousel data including the plurality of sets of broadcast data acquired in the acquiring step; a carousel data broadcasting step for repeatedly broadcasting the carousel data using the carousel method, beginning at an earliest reproduction start time out of a plurality of reproduction start times of the plurality of sets of broadcast data; and an instruction broadcasting step for broadcasting, for each set of broadcast data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of broadcast data at a reproduction start time specified for the set of broadcast data.
With these constructions, broadcast data to be reproduced earlier and broadcast data to be reproduced later in the reception apparatus are repeatedly broadcasted together, and an instruction which indicates to start the reproduction of the latter broadcast data at a reproduction start time specified for the latter broadcast data is broadcasted.
Since the reception apparatus can store the latter broadcast data in a memory beforehand and reproduce it at the reproduction start time, there is almost no delay in reproduction caused by the time taken to receive the latter broadcast data. Thus, the broadcast apparatus can control the timing of changing broadcast data presented to a viewer, with greater precision. The above object can also be fulfilled by a computer program embodied on a computer readable medium for use with a computer, for repeatedly broadcasting broadcast data using a carousel method to a reception apparatus which stores the broadcast data into a memory and reproduces the broadcast data stored in the memory, the computer program including: an acquiring step for acquiring a plurality of sets of program data for each of which a broadcast time slot is specified, and a plurality of sets of additional data which are respectively associated with the plurality of sets of program data; a generating step for generating carousel data including the plurality of sets of additional data acquired in the acquiring step; a data broadcasting step for (a) continuously broadcasting, during a broadcast time slot of each set of program data, the set of program data, and (b) repeatedly broadcasting the carousel data using the carousel method, beginning at the start of an earliest broadcast time slot of a plurality of broadcast time slots of the plurality of sets of program data; and an instruction broadcasting step for broadcasting, for each set of additional data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of additional data at the start of a broadcast time slot specified for a set of program data associated with the set of additional data.
The above object can also be fulfilled by a data broadcast method for repeatedly broadcasting broadcast data using a carousel method to a reception apparatus which stores the broadcast data into a memory and reproduces the broadcast data stored in the memory, the data broadcast method including: an acquiring step for acquiring a plurality of sets of program data for each of which a broadcast time slot is specified, and a plurality of sets of additional data which are respectively associated with the plurality of sets of program data; a generating step for generating carousel data including the plurality of sets of additional data acquired in the acquiring step; a data broadcasting step for (a) continuously broadcasting, during a broadcast time slot of each set of program data, the set of program data, and (b) repeatedly broadcasting the carousel data using the carousel method, beginning at the start of an earliest broadcast time slot of a plurality of broadcast time slots of the plurality of sets of program data; and an instruction broadcasting step for broadcasting, for each set of additional data, a reproduction instruction which indicates to the reception apparatus to start reproduction of the set of additional data at the start of a broadcast time slot specified for a set of program data associated with the set of additional data.
With these constructions, additional data to be reproduced earlier and additional data to be reproduced later in the reception apparatus are repeatedly broadcasted together, and an instruction which indicates to start the reproduction of the latter additional data at the start of a broadcast time slot specified for program data associated with the latter additional data is broadcasted.
Since the reception apparatus can store the latter additional data in a memory beforehand and reproduce it at the start of the broadcast time slot, there is almost no delay in reproduction caused by the time taken to receive the latter additional data.
Thus, the broadcast apparatus can control the timing of changing additional data presented to a viewer, with greater precision.